Tunnel visionThe world's longest tunnel to open 15 October
At 57 kilometers, the Gotthard tunnel, connecting Zurich and Milan, will be the world’s longest tunnel; constructing the tunnel, which opens on 15 October, required the excavation of m an estimated 24 million tons of rock at a cost of $9.5 billion
Constructing an underground tunnel like the Gotthard, which at fifty-seven kilometers long will be the longest worldwide, is a feat of engineering. The challenges of boring such a rail tunnel, which will witness its final breakthrough on 15 October, have been many, and Mother Nature has sometimes made life difficult along the way.
The Gotthard Base Tunnel will be the most important element of the new flat rail link through the Alps. Rising no higher than 550 meters above sea level, the height of the capital Bern, it will reduce the route from Zurich to Milan by one and a half hours.
“For such a huge project you have to construct from different sites because if you start at one portal and then on the other end, you need 20 or more years for the construction of the entire system,” Heinz Ehrbar, chief construction officer with the contractor AlpTransit, told swissinfo.ch. “So we have had in total five different main sites which are in the north, Erstfeld and Amsteg, then in the centre, Sedrun and then Faido and Bodio on the other end.”
These five sites have cut the tunneling time by half. The tunnel is due to open, once it has been fully kitted out, in 2017.
Tunnel vision
The base tunnel is made up of single tubes which are joined every 312 meters with connecting galleries. Trains can change tunnels at the multifunction stations at Sedrun and Faido, which contain ventilation equipment as well as safety and signaling systems.
There are also emergency stop stations every twenty kilometers from where people can escape and be evacuated in the event of a fire or accident.
To make the tunnel, drill and blast methods and giant tunnel boring machines (TBMs) have been used, with TBMs doing around 60 percent of the work.
An estimated 24 million tons of rock will have been excavated on completion of the SFr9.74 billion ($9.5 billion) tunnel.
Kalman Kovari, an emeritus professor of tunneling at the Federal Institute of Technology Zurich and consultant to the project, says that tunneling is not quite as mystical as its reputation. It is simply an engineering activity using natural formations as its material.
No mystery
“Many people think we are exposed to the complete arbitrariness of nature, but this is not correct,” Kovari explained.
Geologists and rock mechanics experts make detailed surveys of the area. The best route is decided and the tunnel is then designed by a group of experts.
Making
